High-Efficiency Millimeter-Wave Single-Ended and Differential Fundamental Oscillators in CMOS

This paper reports an approach to designing compact high-efficiency millimeter-wave fundamental oscillators operating above the $f_{\text {max}}/2$ of the active device. The approach takes full consideration of the nonlinearity of the active device and the finite quality factor of the passive devices to provide an accurate and optimal oscillator design in terms of the output power and efficiency. The 213-GHz single-ended and differential fundamental oscillators in 65-nm CMOS technology are presented to demonstrate the effectiveness of the proposed method. Using a compact capacitive transformer design, the single-ended oscillator achieves 0.79-mW output power per transistor (16 $\mu \text{m}$ ) at 1-V supply and a peak dc-to-RF efficiency of 8.02% ( $V_{\mathrm{ DD}}=0.80$ V) within a core area of 0.0101 mm 2 , and a measured phase noise of −93.4 dBc/Hz at 1-MHz offset. The differential oscillator exhibits approximately the same performance. A 213-GHz fundamental voltage-controlled oscillator (VCO) with a bulk tuning method is also demonstrated in this paper. The measured peak efficiency of the VCO is 6.02% with a tuning range of 2.3% at 0.6-V supply.